Toss

Toss built a financial super app used by more than one in two South Koreans - 94% of people in their 20s, 85% in their 30s. That's the threat surface: a single platform handling payments, banking, insurance, securities, loans, tax filings, and document issuance for tens of millions of users. Over 100 services consolidated into one mobile-first application means credential stuffing, API-layer abuse, and supply-chain compromise aren't theoretical - they're operational baselines the security team has to assume. The company started in 2015 with a simple money transfer service that bypassed Korea's accredited certificate requirement, which itself was a security design decision as much as a UX one. From there, the platform expanded into Toss Securities, shopping, credit score management, and lifestyle services. Each vertical drags in its own regulatory framework - financial, insurance, securities - each with distinct compliance obligations around data protection, transaction integrity, and fraud detection. Securing this means working across mobile app hardening, backend service isolation, real-time fraud analytics, and the infrastructure that ties it all together. Technical domains run deep in mobile-first platform development, financial services technology, and unified financial dashboard engineering. For a cybersecurity team, that translates into securing high-throughput payment pipelines, protecting sensitive financial data at rest and in transit, managing secrets across microservices, and maintaining visibility across a platform where a single compromise could expose banking credentials, investment portfolios, and government-issued document data simultaneously.